*3.1.1 Conditioning*

The formation of a conditioning layer is the initial stage in the development of a biofilm. The components of the bulk fluid settle onto the surface at this stage, developing a substratum. In common, rough surfaces and hydrophobic materials have a preference compared to hydrophilic and smooth surfaces [59]. The microorganism adheres to such surfaces, which are consequently changed to improve a surface charge that assists in the attraction and adhesion of bacteria with opposing charges [60]. The bacteria can adhere to the surface more strongly owing to the existence of pili, fimbriae, and glycocalyx on the surface [61]. Although an initial adhesion can be reversed, if attraction dominates over repulsion, it will become irreversible.
